Strap stretching device



Nov. .21, 1944. F; H. OFING 2,363,328

STRAP STRETCHING DEVICE Filed Nov. 24, 1943 2 Sheets-Sheet l 12 WITNESSES: jg INVENTOR W .5 Fred H Hafzflg 7 BY Z6 67% ATTORNEY Nov. 21, 1944..

F. H. HOFING STRAP STRETCHING- DEVICE Filed Nov. 24, 1943 2 Sheets-Sheet 2 via 7 4,7

PRIOR ART F INVENTOR F7642 H Hafirzg.

a, ATTORNEY WITNESSES! Patented Nov. 21, 1944 UNITED STATES ran: NT, OFFICE I V 2,3sa'as STRAP 'sTaE'romNG DEVICE Fred H. Hfing,S l1ar-psville, Pa., assignorito Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa.,.a corporation of Pennsylvania Application November 24, 1943, Serial No. 511,549

8 Claims- (01. 254-79) My invention relates to devices .for stretching or tightening straps or bands of metal about a substantially solidma'ss and for maintaining a predetermined tension on the strap or band until it is fastened. The invention is adapted for applying steel bands about core structures of transformers Where it is desirable "to applythe band under a predetermined tension to maintain a constant predetermined pressure on thejcore parts enclosed by the band.

Devices for stretching'or tightening a strap'or band around a box or package are known, but

generally these articles about whichthe bandis placed are compressible, 'andthere is no particular reason for maintaining a, predetermined tension of the strap thereon. When the article enclosed by the strap is compressible, no rapid increase in the tension of the strap takes place .upon operation of the stretching device. However, ,When a solid article such as the iron core of a transformer is to be enclosed within ametal strap under a predetermined tension, it becomes necessary to provide for controlling this tension,

since a relatively slight stretching of the strap beyond the desired value will greatly increase the stresses on it and may cause it "to break and failure to bring the strap to the desired tension will cause it to fail in its purpose of maintaining a predetermined desired force on theparts of the core. I

Transformer cores have been made in which the core parts are formed of loops of magnetic material wound layer upon layer and bounded together. The loops are' th'en out to form two .U-shaped core portions which are "assembled about the coils'of the transfiormer and held in place by metal-straps placed about the core'loops. The strap is drawn to a predetermined tension and fastened in'placeto maintain a-desired predetermined'pressure upon the butt joints between the two "U-shaped portions of "the core loop. With the ordinary tool employed for stretching the strap "about the usual type of article, it is d-ifiicult to apply the desired pressure because a very slight increase in the stretchin the strap about the solid mass of "iron greatly increases its tension. If this tension is much too great, the strap will break. If it is not great enough, the strap will not maintain the desired pressure onflthe butt joints. "In a 'copending application of Nick" Mars for Strap stretching devices, filed June 11, -1943, Serial No. 490,442, and assigned to the' 'sa me assignee as the present application, a strap stretching device is described provided ii'ith means {forlockingthe operating mechanism when a predetermined tension on the strap has been effected. In this prior device in which the force, is applied by hand to a lever "carried upon another lever which communicates the force to the operating mechanism, means is provided for locking the second named lever when the force conveyed between the two levers reaches a predeterminedfvalue. It :has been found, however, that in certain cases, such, for example, as when the strap is applied to very small core loops, this tripping of the locking mechanism is at a point on the travel of the operating levers Where the locking pin cannot mesh with the locking rack. If the locking mechanism trip in a position so that the locking pin is opposite a tooth of the locking rack, it is necessaryto stretch the band an additional amount equivalent to the width of one tooth on the locking rack before the, locking device will engage properly.

In accordance with my invention, the lever that is engaged by the hand and directly operated manually, and "from which force is communicated 'to'the second named lever is the one that is locked, so that when the force between the two levers has increased to that value caus- I will not increase the tension above the desired amount.

It is a more particular object of the invention to provide a strap stretching tool of the above indicated character employing a manually operated'member from'which forceis applied to the strap through biasing means that measure the tension on the strap and in providing locking means for the'manually operated member that is operable upon a predetermined force being conveyed through the biasing means .for. locking the manually operated member against operation in either direction and in maintaining pressure on the strap through the biasing means after operation of the locking means.

It is a further object of the invention to 'provide a strap stretching device of :the above indicated character in which the tension on the strap will not be increased above. the desired value because of vfailure of the locking members will be apparent from the following description of a preferred. embodiment of the invention, reference being had to the accompanying drawings,-

in which:

Figure 1 is an elevational view of a core loop with the strap stretching device applied for stretching a steel strap about the loop,

Fig. 2 is a side elevational view of the strap stretching device with a part of the casing removed to illustrate the operating mechanism,

Fig. 3 is a sectional View of a part of the device taken on the line III'III of Fig. 2,,

Fig. 4 is a side elevational view of the strap stretching device with a. portion of the operating mechanism shown in section,

Fig. 5 is a sectional view taken, along the line VV of Fig. 4, with the two operating levers in close position to each other,

Fig. 6 is an end view of the two operating levers in close position to each other, and 7 Figs. 7 and 8 are diagrams illustrating the difference between the operating principle of a prior art device and the device of this invention.

Referring to the drawings and particularly to Fig. 1 thereof, the tool I is shown in position for applying a strap about a core loop 2 com-prising two U-shaped portions 3' and 4 having butt joints between them along the adjoining surfaces 5. The tool is used to apply the metal strap 6 about the core loop under a predetermined tension so as to maintain a continuous pressure between the two U-shaped portions 3 and 4 at the butt joint surfaces 5. As shown, one end 1 of the strap 6 extends over the corner of the core and alon the surface of the loop passing under a fasten ing clip or sleeve 8 and is bent at 9 to return through the clip or sleeve 8 which surrounds the strap, the strap continuing over the end portion I and passing about the core loop and again passing through the clip '8, the end i I being positioned so as to be gripped by the tool for tightening it about the core loop.

After the strap has been pulled tight about the core loop by the tool I, the clip 8, which is in the form of a sleeve or band of metal about the two ends of the strap '6, is crimped r deformed sufficiently so that the edges of the clip and of the two ends of the strap passing through the clip are bent to prevent the strap from loosening.

This is done in a well known manner and is not a part of the invention, and. therefore, is not described in greater detail.

The tool comprises a frame member I2 formed integrally with a handle I3, the frame member including a casing section I4 normally secured to the portion I2 by screws I to form a unitary part of the casing. A lower flat surface I6 of the complementary frame portions I2 and I4 extends horizontally in a plane substantially parallel with the handle I3. The lower portion of the casing section I4 is provided with a foot or flange Il projecting laterally therefrom and which extends horizontally above the surface of the article about which the steel strap is to be stretched. The gripping member I8 mounted on the pivot pin, I9 in the frame structure cooperates. with the upper surface of the flange [l for gripping the end II of the metal strap passing between the members I1 and I8. The member I8 is provided with a serrated gripping lower surface 23 for tightly gripping the strap. The gripping member 18 is normally moved into engagement with the end I I of the strap by means of a coil spring 24 which engages a recess 25 formed in the gripping mem-' bar and bears against a flang 26 formed in the casing portion I4. It will be noted that the position of the grip-ping member I8 is such that as the end II of the strap 9 is pulled toward the right as viewed in Fig. 1, it tends to tighten the grip of the member I8 on the strap and to press it more tightly against the foot or flang IT.

The casing members I2 and I4 are provided with a horizontal guideway which is adapted to receive and guide the movement of a rack bar 28 formed with an enlarged head 29 at one end thereof and provided with teeth 3I on the upper side thereof. The head 29 may be provided with gripping members similar to the members I? and I8 but is shown as provided with a foot or' flange member 32 which is positioned below the end I I of the metal strap and above the other end of the strap to the right of the clip 8 as shown in Fig. 1. An upper member 33 is positioned above the end I I of the strap and mounted on a pin 34 attached to the head 29. The members 32 and 33 provide the jaws of the dnckbill for engaging the end of the clip 8 for forcing the clip in a direction away from the gripping members, I? and I8 mounted on the frame.

The gripping members comprising the parts I! and I8 and the gripping member comprising the parts 32 and 33 form two relatively movable gripping members which are operated away from each other for the purpose of stretching the strap 6 about the core loop. The mechanism for effecting this operation comprises a pinion having teeth for engaging the teeth 3I on the rack bar. This pinion is not shown in the drawings but is integrally attached to the shaft 31 shown in Fig. 2 extending between the two walls of the casing sections I2 and I4 and upon which the ratchet wheel 38 is also fixedly mounted, so that the pin ion (not shown) and the ratchet wheel 38 rotate together. The ratchet wheel 38 is provided with teeth 39 adapted to be engaged by a pawl 42 which is located within the chamber between the I casing members I2 and I4 and pivotally connected by a pin 45 to an extension of an operating lever 46 which is pivotally mounted on a pin 41 carried by the casing members. The upward movement of the lever 46 from the position illustrated in Figs. 1, 2 and 3 causes the pawl 42 to move downwardly in engagement with the teeth 39 of the ratchet wheel to move the ratchet wheel 38 and the pinion engaging the teeth 3| in a clockwise direction to move the head 29 of the rack bar toward th left as shown in the drawings.

The pawl 42 is normally held in engagement with the teeth 39 of the ratchet wheel by a spring 48 mounted about a pin 49, the lower end of which is positioned in a socket 5| formed in the upper side of a detent 52 which is pivotally mounted on a pin 53 mounted in the casing structure. The detent 52 is provided with a tooth 54 adapted to engage the teeth 39 of the ratchet wheel .to prevent reverse rotation thereof. The upper end of the pin 49 extends through a bore in a projecting head 56 forming a part of the pawl 42. The lower end of the spring 48 engages a collar 51 on the pin 49 and the upper end of the spring 48 engages the projecting head 56. When the pawl is operated to rotate the ratchet wheel 38 the detent 52 rides over the teeth 39 of th ratchet, wheel and engages a tooth in a new position to hold the ratchet wheel against reversed rotation during a reverse movement of the pawl 42.

To permit, the release of the ratchet wheel and to allow a reverse movement of the ratchet wheel 38 and pinion and a return movement of the head 29-.toward the frame, after these parts :have been actuated .to reflect :the desired :stretching of the steel .strap 15, the .detent :52 :is :moved upwardly about its pivot 53 and the pawl 42 is simultanethe underside .of the .detent .52 .and provided also with an upwardly extending part 6.3 which serves as acam to effect movement of the pawl42 away fromengagement with the teeth 89 of theratchet wheel. Any suitable :means may be provided for rotating the shaft =61 in va'clockwise direction .to effect the release of the pawl 42 and the detent 52 to engage the teeth of the ratchet wheel .38.

In order to provide for limiting the pressure or tension to be applied to the steelstrapt, a second lever 1.0 is provided having one endmounted onthe pivot 4'! .upon which the lever '46 ,is mounted. The lever is provided with side flanges ll extending upwardly on the opposit sides of the lever 46 when the two are brought into close relation. The .body portion 12 of the lever is provided with bores or sockets 16 o posite simi+ lar bores 17 in the underside of the 1ever48. and between which coil springs 18 are positioned with their opposite ends in the bores 16 and H.

A locking member .81 is provided and is shown as having a cylindrical shaft portion 82 extending through a bore 83in the body of the lever 18 for slidable endwise movement therein, The locking member 8| is provided with a tooth 84 that is adapted to engage between the teeth on. the rack member 14 and is provided also with an outer member 85 extending along the side of the rack 14 for providing ready manual operation of the locking member to release the tooth 84 from engagement With the rack teeth 15. A spring 86 is provided about the outer end portion of the shaft 82 in anenlarged portion of the bore 83, one end of the spring engaging an abutment 81 and the other end engaging the flange 88 on the shaftBZ adjacent the tooth 84 for biasing the locking member 8! outwardly to case engagement of the teeth 84 and 15. As best shown in Fig. .5, a spring clip .9I is provided within a bore in the body portion 12 shown attached thereto at 92 and having the end 93. extending across the lower side of the shaft 82 to engage serrations therein at 94 to hold the shaft 82 in the position illustrated in Fig. 4 with the tooth 84 out of engagement with the teeth 15. A pin 95 is provided within a bore 96 in the body portion 12 of the lever-l0, the lowerend of which extends through a slot 91 in the shaft 82. The upper end of the pin 95 extends upwardly above the upper surface extending through :the clip =8 and bent at:9 under the main :body .of the :strap .6 and the outer 1 end il .l oi-thestrapextending through the clip 8 between the bodies 32 and 83 of the tooth :and gripped between the members 18 and H, the tool is ready for operation to stretch the strap 6 about the core loop 2. The locking-member 81 is then :in the unlocked position as illustrated in Fig.4 with-the shaft 82 being held :in the unlocked position by of the body portion 12 of th lever 19 and is 130- sitioned to engage the lower end of a set screw 98, shown as screw threadedly fixed in position in the upper lever 46 and held in a desired position by a nut 99. By varying the extent of the projection of the lower end of the set screw. .98 below the lower surface 'of the lever ',46, the relative position of the levers 10 and 46 at which the set screw 98 will engage the pin 95 may be'varied. Eventually, as the levers are brought into closer relationship, the setscrew 98 will cause the pin 95 to be pressed. downwardly sufficiently to release the end 93 of the spring clip 9| from the serrations 94 in the shaft 82 to permit the shaft to be operated by' thespring 86, causing the tooth 84 to lock between the teeth 15 of the rack I4.

After the steel strap has been positioned about 8 the core loop, as shown in Fig. 1, and the end 1 the end 93 of the spring clip 9|. The hand of the operator. is then grasped about the handle 13 and the lower portion of the secondary lever 10 and the fingers successively compressed to effect successive upward movement of the levers Ti! and :46 to cause successive lowering and raising-of the pawl'42 to operate the ratchet wheel 38 in a clockwise direction as viewed in Fig. 2, this motion being communicated through the pinion and theteeth 8'! on the rack'bar 28 to cause the head 29 of the tool to move toward the left as illustrated in the drawings, or away from the frame .portion of the tool. The end ll of the steel strap slides between the members 82 and 33, which members force the clip 8 toward the left, the end ll of the strap being held by the members l1 and l 8 as the strap is tightened about the The force applied to the lever 18 is conveyed to the lever 46 through the springs 7-8. As the strap tightens about the core, the force necessary for successive movements of the pawl 82 increases so'that the force conveyed from the lever H!v to the lever 48 correspondingly increases. The lever 8 comes closer to the lever 48 and upon the transmission of a predetermined force between the two levers, the pin -95 is moved downwardly by the set screw 98, forcing the end 93 of the retaining spring from engagement with the shaft 82 permitting the shaft to "be operated by the spring "88 toward the right, as viewed. in Fig. 4, causing the tooth 84 to engage between teeth 95 of the rack '14 to lock the leversystern against-further movement of the-"pawl 42 and further tightening of the strap. In the'locked position, the force communicated from the lever Hithrough the lever 4s and the pawl 42 is continuously applied through the springs 18; thus preventing locking the lever system in ,a position where a much higher force than that desired is appliedto thestrapas is possible where 'theleVer 48 is locked instead of the lever "10,. This will 'be understood by comparing the diagrammatic showing of the two different applications of the locking means in the lever system as shown in Figs. 7 and 8.

Fig. 7-is a diagrammatic view of a 'lever'system in which the lever 48 is locked, whena predetermined force is communicated from the lever .19

to the lever 46 through the spring members 18.

In thesystem diagrammatically illustrated in Fig. 7, the locking device 8| is carried on the lever 48 and when released locks the lever 46 in a fixed position, thus applying a force to the pawl 42 dependent upon this position. Since the lever 48 may be required to move slightly due .to the tooth 84striking one of the teeth after the force through the springs '18 has reached a value stretching device is a relatively larger proportion of the length of thestrap about the loop than would be the case in a larger loop employing a longer strap. Fig. 8 diagrammatically illustrates the arrangement of the lever system; and locking mechanism illustrated in Figs. 1 to. 6, in which the locking mechanism is carried on the lever 10 and the force applied to the pawl 42 is communicated from the lever 10 through the springs '18 to the lever 46 after the lever 10 has been locked, so as to cushion or weigh the force thus applied, and thus prevent an undue increase in this force above the force between the two levers required to release the locking mechanism.

It will be seen that in the mechanism disclosed as illustrating an embodiment of my invention, if the locking pin 84 is tripped when the lever '|0 carrying it is in a position such that it will engage the end of tooth of the locking rack, so that it is necessary to move the lever 10 further to permit the pin 84 to engage between two adjacent teeth 15 on the rack, the springs 18 between the two levers 46 and 10 will absorb the additional movement of the lever 10 required for the locking pin to engage between the teeth 15 and no substantial increase in the force applied to the band will result.

It will be understood by those slgilled in the art that modifications may be made in the details of the structure illustrated and described without departing from the spirit of my invention, and it is intended that the above description of a preferred embodiment of the invention be taken as illustrative of the invention and not in a limiting sense.

I claim as my invention:

1. The combination ina strap stretching device, of a pair of relatively movable members, means carried by each of said relatively movable members and constructed to grip the ends of a flat metal strap with said ends overlapping one above the other, and means for moving said relatively movable members away from each other for drawing the strap taut about an article and maintaining said overlapping portions in taut condition, a pair of levers mounted at their inner ends on the frame of the device and extending outwardly therefrom in the same general direction, a plurality of compressible members positioned between said two levers and spaced at intervals along the length thereof for transferring force applied to one of said levers to the other of said levers for operating the stretching device, and means operable upon the application of a predetermined force between said levers for looking the lever to which the force is first applied against further movement.

2. The combination in a strap stretching device of a frame, a rackbar having movement in said frame, means carried by said bar and said frame for engaging a strap, means carried by said frame including a ratchet wheel for effecting movement of said rack bar relative to said frame, a pawl adapted to engage said ratchet wheel, a handle mounted in fixed position on said frame, a lever pivotally mounted at its inner end on the frame of said device for operating said pawl, a second lever pivotally mounted adjacent the inner end of the first named lever and extending outwardly along the first named lever and adapted to be manually engaged and operated, a plurality of spring members positioned between said two levers and spaced at intervals along the lengths thereof for transferring force from the manually engaged second named lever to the first named lever for operating the stretching device,

and means operable upon the application of a predetermined force between said levers for looking said second named lever against further movement.

3. The combination in a strap stretching device, a pair of relatively movable members, means carried by each of said relatively movable mem- "bers and constructed to grip the ends of a fiat metal strap with said ends overlapping one above the other, and means for moving said relatively movable members away from each other for drawing said strap taut around an article .and maintaining said overlapping portions in taut condition including a lever pivotally mounted at its inner end on the frame of the device, a lever pivotally mounted adjacent the inner end of the first named lever and extending outwardly along the first named lever, the second lever having side portionsspaced to move along opposite sides of the first named lever and a body portion connecting the side portions, a plurality of recesses along the adjacent sides of the two levers and spring members having their opposite ends in the recesses in the two levers for biasing the two levers away from each other, and means operable upon the application of a predetermined force between the two levers for locking the lever to which the force is first applied against further movement for holding the device in locked position with a predetermined force on the strap that is applied continuously through the springs between the two levers after the one lever is locked.

4. The combination in a strap stretching device, a pair means carried by each of said relatively movable members and constructed to grip the ends of a fiat metal strap with said ends overlapping one above the other, and means for moving said relatively movable members away from each other for, drawing said strap taut around an article and maintaining said overlapping portions in taut condition including a lever pivotally mounted at its inner end on the frame of the device, a second lever pivotally mounted adjacent the inner end of the first named lever and extending outwardly along the first named lever and adapted to be manually engaged and operated having spring means between the two levers for biasing the two levers away from each other and for communicating force applied to the manually operated second named lever to the first named lever for operating the relatively movable members, and means operable upon the application of a predetermined force between the two levers for locking the lever to which the force is first applied against further movement for holding the device in locked position with a predetermined force on the strap that is applied continuously through the spring means between the two levers after the one lever is locked.

5. The combination in a strap stretching device, of a pair of relatively movable members, means carried by each of said relatively movable members and constructed to grip the ends of a flat metal strap with said ends overlapping one above the other, and means for moving said relatively movable members away from each other for drawing said strap taut around an article and maintaining said overlapping portions in taut condition comprising a lever pivotally mounted at its inner end on the frame of said device, a second lever pivotally mounted adjacent the inner end of the first named lever and extending outwardly along the first named lever of relatively movable members,

, application of a predetermined force between said levers for locking said second named lever against further movement, said means including a locking member slidably mounted on said second named lever and biased for movement out-' wardly from the pivotal support of the lever, a rack extending along the path of travel of the outer end of the lever and provided with teeth 'for receiving the locking member, a latch member normally retaining the locking member from engagement with the rack, and means for trip ping the latch member upon a pretermined relative movement of the two levers upon compression of the biasing means between them for holding the device in locked position witha predetermined force on the straptha-t is applied continuously through the spring means between the two levers after the one lever is locked.

6. The combination in a strap stretching device, of a pair of relatively movable members, means carried by each of said relatively movable members and constructedto gripthe ends of a flat metal strap with said ends overlapping one above the other, and means for moving said relatively movable members away from each other for drawing said strap taut around an article and maintaining said overlapping portions in.

taut condition including a pair of levers mounted at their inner ends on the frame of the device and extending outwardly therefrom in the same general direction, spring means positioned for transferring force between the two levers for operating the stretching device, and a single locking means operable upon the application of a predetermined force between said levers for locking one of said levers against further move ment in either direction for holding a predetermined force on the strap that is applied continuously through, the spring means between the two levers after the one lever is locked.

said frame including a ratchet wheel for effecting movement of said rack bar relative to said frame, a pawl adapted to engage said ratchet wheel, a handle mounted in fixed position on said frame, a lever pivotally mounted on its inner end on the frame of said device for operating said pawl, a second named lever pivotally mounted adjacent the inner end of the first named lever and extending outwardly along the first named lever, a spring member positioned for transferring force from the second named lever to the first named lever for operating the stretching device, and a single locking means operablev upon the application of a predetermined force between said levers for locking said second named lever against further movement in either directionfor holding the device in looking position with a predetermined force on the strap that is applied continuously through the spring member between the two levers after the one lever is locked. I I

8. The combination in a strap-stretching device, of a pair of relatively movable members, means carried by each of said relatively movable members and constructed to grip the ends of a flat metal strap with said ends overlapping one above the other, and means for moving said relatively movable members away from each other for drawing said strap taut around an article and maintaining said overlapping portions in taut condition including a lever pivotally mounted at its inner end on the frame of said device, a second lever pivotally mounted adjacent the inner end of the first named lever and extending out-. wardly along the first named lever for operating the first named lever, biasing means positioned for transferring force from the second named lever to the first named lever for operating the erable upon the application of a predetermined I force between said levers for locking said second 7. The combination in a strap-stretching device, of a frame, a rack bar having movement in,

said bar and said means carried by locked.

named lever against further movement in either direction for holding the device in locked position with a predetermined force on the strap that is applied continuously through the biasing means between the two levers after the one lever is FRED H. HOFING. I 

